This invention relates to a thermo-compression bonding apparatus for connecting electrode terminals of a liquid crystal panel to electrode terminals of an external drive circuit (referred to below as TCP).
An anistropic conductive film (referred to below as ACF) that is a thermosetting resin is normally used for connecting electrode terminals on a TCP film and the electrode terminals extending on the substrate to the outside from the edge of the liquid crystal (LC) panel. This connection is accomplished by temporarily bonding and holding the substrate, having the electrode terminals extending from the edge of the LC panel, laminated with the film on which the TCP electrode terminals are formed with the ACF therebetween. Pressure is then applied so as to thermo-compression bond this laminate.
A thermo-compression bonding apparatus is generally used for this connection. Then, when color LC panels were introduced, the number of TCP tripled compared with black and white LC panels. As a result, a method of simultaneously thermo-compression bonding plural TCP on one side of the LC panel has been used to shorten the connection time.
However, various new problems arise when all TCP on one side are simultaneously connected to the substrate. One of these problems is the problem of offset when bonding the LC panel electrode terminals and the TCP electrode terminals. In order to solve this problem, a semiconductor device connecting apparatus is disclosed as a conventional semiconductor device connecting apparatus in Japanese Patent Publication Tokkai Hei 7-130795 (130795/1995).
In the conventional semiconductor device connecting apparatus as will be described later, it should be noted that while the center of a long pressure head is pushed by a pneumatic cylinder to apply pressure to TCP arranged on the stage, the center of the pressure head is pushed by the pneumatic cylinder by way of a freely turning pin, and it uniformly contacts the surface of the variable temperature stage with the above noted semiconductor device connection apparatus, the force of the pressure is concentrated in the middle of the rod-shaped pressure head, causing the middle of the long pressure head to bend and deflect. As a result, the TCP positioned in the middle of the pressure head is pressurized by a vertical pressure force, but a partial force diagonal to the stage surface occurs in the pressure on the TCP positioned at both sides of the pressure head, and there is the danger of an offset between the TCP electrode terminals and the electrode terminals of the substrate.
Furthermore, when TCP size or count changes, the heat capacity of the overlapping part naturally also changes, and the thermo-compression bonding time changes. For example, when TCP size increases, the heat capacity of the overlapping part also increases, and the time required to reach the resin setting temperature increases. If the temperature of the variable temperature stage is set high in this case to speed the temperature rise time, the polarization plate of the LC panel adjacent to the variable temperature stage will be burnt by heat radiation from the variable temperature stage.
It is also difficult to maintain a uniform temperature in the placement surface of a long variable temperature stage having no indication of whether a temperature sensor is present or where it is located. Furthermore, even if temperature control of the variable temperature stage is possible, it is not possible to determine whether the TCP, ACF, and substrate layer arranged on the placement surface of the variable temperature stage have reached a desired temperature, presenting the problem that there could be TCP not bonded with the substrate layer.
An object of this invention is to provide a thermo-compression bonding apparatus and thermo-compression bonding method that can connect the electrode terminals of a substrate and the electrode terminals of TCP without the electrode terminals shifting or the polarization plate burning by holding uniformly at a desired temperature and uniformly applying pressure to a laminate of TCP, ACF, and a substrate layer.
According to an aspect of this invention, there is provided a thermo-compression bonding apparatus comprising a backup part on which a plurality of laminate members are arranged in a longitudinal direction of the backup part, and a compression bonding head with an internal heater for applying pressure to the laminate members placed on the backup part while heating the laminate members. The laminate members are formed by overlapping and temporarily fixing electrode terminals of a substrate extending from an edge of a liquid crystal panel and electrode terminals of an external drive circuit with an anistropic conductive film therebetween. The thermo-compression bonding apparatus comprises a vertically movable plate for moving the compression bonding head towards a vertical direction, a pneumatic cylinder for linking a piston rod to the vertically movable plate to applying a pressure to the compression bonding head, and auxiliary heating means disposed to the backup part at a position opposite to the liquid crystal panel for auxiliary heating the laminate members which are heated by the compression bonding head.
According to another aspect of this invention, there is provided a method of connecting liquid crystal panel electrode terminals to external drive circuit electrode terminals by thermo-compression. The method comprises the steps of (A) compressing laminate members by a compression bonding head whose temperature is kept at a predetermined temperature, to heat the laminate members to the predetermined temperature, the laminate members being formed by overlapping and temporarily fixing electrode terminals of a substrate extending from an edge of a liquid crystal panel and electrode terminals of an external drive circuit with an anistropic conductive film therebetween, (B) making the temperature of the laminate members be kept at a desired temperature by auxiliary heating means for auxiliary heating the laminate members which are heated by the compression bonding head, and (C) connecting the liquid crystal panel electrode terminals to the external drive circuit electrode terminals.